Convert String to Double in Java

String to Double in Java

In this lecture we will see the String to Double conversion. There are three ways to convert a String into a double.

1: Using Double.parseDouble

public static double parseDouble(String str) throws NumberFormatException

It returns the double value represented by the string argument and throws following exceptions:

NullPointerException – if the specified String str is null.
NumberFormatException – if the string format is not valid.  For example
If the string is “122.20ab” this exception will be thrown.

String strg="222.102";
Double var= Double.parseDouble(str);

Double variable var value would be 222.102 after conversion.

2: Using Double.valueOf

String strg1="222.102";
 Double var1= Double.valueOf(strg1);

The value of var1 would be 222.102

3: Double class constructor

String strg2="222.102";
Double var2= new Double(strg2);

Double class has a constructor which parses the passed String argument and returns a double value.

public Double(String s) throws NumberFormatException

Constructs a newly allocated Double object that represents the floating-point value of type double represented by the string.

Example:

public class Example{
   public static void main(String args[]){
       //Using parseDouble
       String strg="222.102";
       Double var= Double.parseDouble(strg);
       System.out.println(var);

       String strg1="222.102";
       Double var1= new Double(strg1);
       System.out.println(var1);

       //Using valueOf method

       String strg2="122.202";
       Double var2= Double.valueOf(strg2);
       System.out.println(var2);
   }
}

Output:

122.202
122.202
122.202